The power supply is a very basic and important component of an electronic circuit. A common power supply has a main output branch, a plurality of auxiliary output branches and a feedback circuit for the main output branch. Accordingly, only the main output branch is provided with a feedback process, and thus has a good load response speed; however, due to lack of a feedback process, the auxiliary output branches have a poor load response speed, which may result in the undervoltage phenomena, and affect normal operation of the circuit.
In view of the technical problem, an existing solution is to increase the number and capacitance of the capacitors in the auxiliary output branches. A sufficiently large capacitance allows the auxiliary output branches to have a sufficiently long hold-up time, thereby lowering the probability of the undervoltage event on the auxiliary output branches. Such a solution has a simple circuit structure, but fails to fundamentally solve the problem and merely lowers the probability of faults. Besides, when there area greater number of capacitors, they take up a larger space to be disposed, which affects the power density, and the cost will increase.
Accordingly, it is needed to provide a feedback device for a power supply that not only fundamentally solves undervoltage problems but also ensures the power density.